Flashcards in Week 9 - Circulation - finished Deck (37):
How long does it take for neuro SSx to appear after ischemia in the brain?
What does the blood deliver to the brain?
O2 and glucose
Can the brain use anything but glucose for energy?
What does the blood remove from the brain?
It removes lactic acid and CO2, which can become neurotoxic if they build up
Information about the regulation of blood and O2 content of blood to the brain:
The CNS self regulates the delivery and distribution of blood by sensing the momentary pressure changes in its main arteries of supply, the internal carotids. It controls the arterial oxygen tension by monitoring respiratory gas levels in the internal carotid artery and in the cerebrospinal fluid (CSF) near the medulla oblongata. The control systems used by the brain are exquisitely sensitive and sophisticated, but they can be rendered useless when a distributing artery spontaneously ruptures or is slammed shut by an embolus.
Stroke is the number what cause of death in the western world?
What % of body mass does the brain account for?
How much of our CO does the brain receive?
What % of total O2 consumption does the brain account for?
What are the 2 types of stroke?
Haemorrhagic and occlusive
What are the major arteries that supply the brain? How do these arteries supply the whole brain?
Anterior Cerebral Artery
Posterior Cerebral Artery
Middle Cerebral Artery
These 3 arteries anastomose to protect and supply the superficial aspect of each hemisphere. From there superficial arteries, smaller penetrating arteries arise to supply deeper structures. For the most part, these deeper areas are the end zones and receive no collateral supply.
What are the major inputs to the circle of Willis?
The internal carotid arteries and the vertebral arteries
Is the circle of Willis always anatomically the same in every person?
No, it is one of the most anaotmically variable places in the body.
Where do the vertebral arteries fuse and what do they fuse into
They fuse at the pontomedullary junction and fuse into the basilar artery.
Is it the anterior or the middle cerebral artery that is the direct continuation of the internal carotid arteries?
The middle. The anterior cerebral artery is the branch off the internal carotid artery.
Why is the middle cerebral artery the most likely place for a stroke/an embolism to go?
Because it is the direct continuation of the internal carotid, so the embolism will most likely just flow directly along the artery, rather than possibly going through the branch for the anterior cerebral artery.
What are the SSX of middle cerebral artery infarction? (heaps so just name a few and understand the part fo the brain the MCA supplies and what the affects may be)
Contralateral weakness and sensory loss
Mostly affecting face and arms due to somatotropic organisation of pre and post central gyri
Distal limbs affected more so than proximal as the trunk and proximal limbs appear to have some level of bilateral cortical coding (PMA and SMA)
Forehead, pharynx and jaw also have bilateral representation
Often period of hypotonia which progresses to spasticity with hyperreflexia
Proprioceptive and discrimination are often lost giving rise to ataxia
Pain and temp sensation are often altered but are rarely lost
Vision is often impaired due to damage to the optic radiations:
- parietal: inferior quadrantanopsia
- temporal: superior quadrantanopsia
(divisions of the MCA in the visual area, only one quarter of the visual field will be lost)
Depending of the hemisphere affected there may also be disturbances of language or spatial perception
Dominant hemisphere: difficulties with language may present as a Broca's, Werknicke's or global aphasia (cannot produce or interpret speech)
Parietal damage may cause motor apraxias (loss of motor pattern of something that they have done a lot of times e.g. doing up a button)
Neurologial deficit may be more specific if one of the end zone has been affected.
SSX of anterior cerebral artery infarction:
Motor and sensory phenomena but tend to be the contralateral leg, most profoundly the distal limb
Maybe urinary incontinence (due to motor cortex destruction or destruction of the area which codes specifically for the inhibition of bladder emptying
Maybe speech distrurbances
Sympathetic motor apraxia may arise from the damage to the corpus callosum which connects the cortex to the contralateral motor cortex.
The anterior cerebral is more commonly associated with bilateral infarcts than the other cerebral arteries due to the common congenital malformation of both arteries arising from a single trunk
Bilateral infarct often gives rise to severe behavioural disturbances and personality changes which may even include muteness
SSX of the posterior cerebral artery
Unilateral destruction of the calcarine cortex, in some cases which may even be bilateral if occluded at the point of bifurcation.
Macular vision will typically be spared due to the common supply by the MCA. The peripheral vision will be gone, by the central vision will be in tact.
The thalamus may be affected giving hemisensory loss and spontaneous pain.
Subthalamic nucleusmay be affected giving contralateral hemiballismus
Midbrain may be affected giving ipsilateral oculomotor palsy and contralateral hemiparesis or ataxia.
Spinal cord circulation, what is it supplied by.
2 posterior spinal arteries and one anterior spinal artery.
What is the anterior spinal artery a branch of?
A branch of the vertebral arteries
What does the anterior and posterior spinal artery supply?
Anterior spinal arteries:
Supplies the ant. 2/3 of the cord
Including the ant. and lat. horns
Supplies anterior inferior part of the medulla including the pyramids, medial lemniscus and some of the CN XII fibres
Posterior spinal arteries:
In combination supply the posterior 1/3 of the cord
This includes the dorsal horns and columns
At the level of the medulla supply the dorsal column nuclei also
Do the anterior and posterior spinal arteries adequately supply the whole spinal cord?
No, only the Cx segments. After that radicular arteries compensate.
What do the radicular arteries supply? Where do they arise from? How do they enter the vertebral canal?
Supply each level via the anterior and posterior spinal a.’s
They also supply the vertebrae and meninges
Arise from spinal branches of the vertebral, deep Cx, ascending Cx, posterior intercostal, Lx & lateral sacral a.’s
Follow the spinal nerves and divide into dorsal and ventral along the line of the spinal n. roots, hence they enter the vertebral canal via the IVF
What does the greater radicular artery supply?
Makes a great contribution to the anterior spinal a. and provides most of the blood supply to the inferior 2/3 of the spinal cord
Much larger than the other radicular vessels
What are the main arteries that supply the brainstem?
Dorsolateral Medulla: PICA
Anterior Medulla: anterior spinal and vertebral arteries
Pons: basilar branches
- Basilar artery
- Superior Cerebellar artery
What are the posterior vertebral arteries a branch of?
The posterior inferior cerebellar artery
Where does the PICA arise from?
Typically arise from the vertebral a.’s but may come from the basilar
What does the PICA give rise to?
Typically give rise to the posterior spinal a.’s
What does the PICA supply?
Supplies the dorsolateral zone of the medulla, the inferior portion of the cerebellum and the choroid plexus of the 4th ventricle, stroke gives rise to Wallenberg’s syndrome
Medial and inferior vestibular nuclei
Inferior cerebellar peduncle
Nucleus ambiguus & intra-axial fibres of CN IX & X
Spinal trigeminal nucleus & tract
Hypothalamospinal tract to give Horner’s syndrome
What is the basilar artery formed by and where does this happen?
Is formed by the vertebral a.’s at the pontomedullary junction
What does the basilar artery give rise to?
Gives rise to the pontine a.’s, AICA + the labyrinthine a. and the superior cerebellar a.’s
What do the pontine arteries supply?
Supply the cortiospinal tracts at the pontine level and the fibres of CN VI
What does the AICA give rise to?
Typically gives rise to the labyrinthine a. for the supply of the cochlea and vestibular apparatus
What does the AICA supply?
Supplies the inferior surface of the cerebellum, the nucleus and intra-axial fibres of CN VII, spinal trigeminal nucleus and tract, vestibluar nuclei, cochlear nuclei, intra-axial fibres of CN VIII, ALS and the inferior & middle cerebellar peduncles
Also contributes to the supply of the hypothalamospinal tract
Where does the superior cerebellar artery arise from?
The Basilar artery